Free flight print system for a serial printer

ABSTRACT

A serial printer print head rotates about a fixed axis and moves toward a multiple fold print medium in a controlled free flight manner. The print head is mounted on a yoke support which in turn freely rests on a movable armature. Both the yoke and the armature pivot about a fixed axis which intersects structure used to position the print head. The positioning structure itself is flexible at the pivotal point so as to introduce a minimum amount of spring energy. The yoke is constantly biased so as to result in a controlled free flight when it lifts off the armature plate.

United States Patent Bath et al. Sept. 25, 1973 FREE FLIGHT PRINT SYSTEM FOR A 3,286,806 11/1966 Schoenfelder 197/55 x SERIAL pRINTER 3,355,000 11/1967 Blodgett 197/17 [75] Inventors: James G. Bath, Hudson; Steven P. i of Massfizz-215232121671: ssdtfi [73] Assignee: Honeywell Information Systems Inc., Attorney-Ronald T. Reiling et a1.

Waltham, Mass.

[22] Filed: 7 Aug. 25, 1971 [57] ABSTRACT [21 App]. No.: 174,821 A serial printer print head rotates about a fixed axis and moves toward a multiple fold print medium in a con- 52 us. c1. 197/55 free nigh i The Prim head is mmmed on a yoke support WhlCh in turn freely rests on a mov- [51] Int. Cl B413 l/32 able armature. Both the yoke and the armature pivot [58] Field of Search 197/55, 17, 18,

101/93 C about a fixed axis which Intersects structure used to po sition the print head. The positioning structure itself is 56] References Cited flexible at the pivotal point so as to introduce a mini- I mum amount of spring energy. The yoke 15 constantly UNITED- STATES PATENTS biased so as to result in a controlled free flight when it 2,787,210 4/1957 Shepard 101/93 lifts off the armature plate. 1 3,168,182 2/1965 Bernard et a1..... 197/18 X 3,221,863 12/1965 Pietzsch 197/55 X 13 Claims, 6 Drawing Figures E [-1 I [F j i I O-4 T [T 1s 1 .L 1 l E+ -1 1- V J 1 32 24 IO 28 l o J T 38 48 PAIENTEUSEP25I975 3.760.926

' sum 2 or .2

FIGURE 4 FIGURE 5 PRINT ENERGY REQUIRED FOR IMPACT PRINTING A LARGE LAND CHARACTER ON A 6 PART FOLD OF 5 PRINT MEDIUM 5 4 PART PRINT ENERGY REQUIRED FOR E 3 PART I A 1 PART FOLD OF PRINT (L 2 PART MEDIUM DISTANCE TRAVELED BEFORE IMPACT INVENTORS JAMES C.BATH STEVEN P. CAHILL ATTORNEY FREE FLIGHT PRINT SYSTEM FOR A SERIAL PRINTER BACKGROUND OF THE INVENTION The present invention relates to serial printers, and in particular to apparatus for impacting the serial printer print head.

This application is related to co-pending U.S. Application Ser. No. 94,034, filed on Dec. 1, 1970 in the names of Pateuk et a1; entitled Intemal Actuator for Impacting a Serial Printer Print Head.

According to the print system of U.S. Application Ser. No. 94,034, a serial printer print head is caused to be continually driven into the print medium during each impact print stroke. The print medium must therefore absorb the total amount of impact force from the driven print head. This may result in a blurring of the print and possible degradation of the print medium itself under the excessive duration of forced impact. The present invention seeks to erradicate the problems posed by the continuous drive of the print head of the aforementioned U.S. Application by introducing a novel free flight system.

The concept of"free flight impact printing of a character with a print medium has been previously introduced in printers. Various mechanisms have evolved for accomplishing the free flight impacting of a print head in a serial printer. Some of these mechanisms are directed towards the flexing of a support which the print head is connected to. This introduces a considerable amount of stored energy into the flexed support which produces almost the same amount of blurred printing and excessive impacting that exists in the continually applied impact force printers. Other types of serial printer mechanisms have attempted to introduce pure free flight byallowing the print head to essentially impact the print medium without any restriction whatsoever. This results in a further need for the recapturing of the print head immediately following impact so as to prevent multiple bouncing by the print head. This latter type of mechanism results in a significant number of moving parts for recapturing the print head all of which have various tolerances which tend to compound and reduce over-all system capability.

The present invention therefore has as an object to provide a serial printer with a print head mechanism that introduces negligible stored energy into the positioning apparatus as a result of flexing it during the free flight" impact stroke. I

It is another object of this invention to provide a quickly responsive free flight print system which contains a minimum number of moving parts.

It is a still further object of this invention to provide a free flight print system wherein the print head remains partially controlled during free flight.

SUMMARY OF THE INVENTION To achieve the above-mentioned objects, the present invention provides an impact mechanism for a serial printer print head wherein the printhead is launched into a controlled free flight print stroke essentially free of any external force considerations except for a bias spring arrangement. The impact mechanism contains a small number of moving parts which include a yoke that rests against a pivotal armature that is magnetically attracted by an electromagnet. The yoke and armature are made to pivot about the same axis of rotation. The

armature first travels against the electromagnet and then the yoke lifts off the armature and carries the attached print head toward the print medium in free flight. The print head is constantly biased in its pivotal travel toward the print medium by a spring means so as to provide a measure of control over the free flight of the print head. The positioning shaft structure is made extremely flexible at the point about which it is required to flex or bend to thus introduce negligible spring energy into the system.

BRIEF DESCRIPT ION OF THE DRAWINGS For a better understanding of the present invention, reference should be made to the accompanying drawings wherein:

FIG. 1 is a side elevational view, partially in section, showing an impact apparatus, a print head, and a representative print medium backed by a platen.

FIG. 2 is a top view of the impact apparatus of FIG. 1 illustratively showing the pivotal axis and yoke structure of the impact apparatus.

FIG. 3 is a sectional view along the line 33 of FIG. 1 showing the cooperation between the positioning structure for the print head and the pivotal axis.

FIG. 4 is a side elevational view of the impact apparatus illustratively showing the print head in a first position during a typical impact stroke.

FIG. 5 is a side elevational view of the impact apparatus illustratively showing the print head and impact mechanism in a second position during a typical impact stroke.

print head during a typical impact stroke.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a print head 10 which is movable in both an axial direction 12 and a rotational direction 14 so as to position a given character 16 for impact printing. The positioned character 16 is to be impact printed through an ink ribbon 18 onto a multiple fold print medium 20 that is backed by a platen 22. The multiple fold print medium 20 is to be understood as encompassing anything from a single part fold to a six part fold of normal computer printout paper.

The impact apparatus of the present invention begins with a cylindrical neck 24 which houses both the rotary and axial drive shafting used to position the print head 10. As can be seen from F IG. 1, the cylindrical neck 24 extends substantially into the print head 10. This particular type of internal actuator arrangement is shown and fully described in U.S. Application Ser. No. 94,034, tiled in Dec. 1, 1970 in the names of C. J. Pateuk and H. M. Shneider. The cylindrical neck 24 extends down to and is part of a yoke 26 which is pivotal about a set of pins 28 and 30 as shown in FIGS. 1 and 3. The yoke 26 extends back from the pins 28 and 30 in the form of a set of arms 32 and 34 to either side of an electromagnet 36. The yoke arms 32 and 34 as shown in FIGS. 1 and 2 rest on an armature plate 38 which is in turn pivotal about pins 28 and 30 by a set of shoulders 40 and 42 as shown in FIGS. 2 and 3. It is seen that both the yoke 24 and the armature plate 38 pivot about the pins 28 and 30. The pins 28 and 30 thus define a common pivotal axis 44 which extends through them as shown in FIGS. 2 and 3. The pivotal axis 44 is seen to be fixed relative to a base 46 via a set of mounting posts 48 and 50 as shown in FIGS. 2 and 3. The base '46 constitutes part of an overall carriage apparatus which moves the head in the direction in which the line of print is being formed, as is common in serial printers.

Referring to FIG. 1, the armature 38 is seen to rest on an energy sink pad 52 which is inclined at an angle of one degree to the horizontal. This results in a one degree inclination of the armature 38 with respect to the bottom horizontal surface of the electromagnet 36 so as to define a one degree gap there-between. The yoke arms 32 and 34 are also contoured to the one degree inclination of the armature 38 so as to normally maintain the print head in a vertical upright position. This latter feature allows the print character 16 to be positioned by a perfectly straight, and well supported shafting within both the print head 10 and the cylindrical neck 24.

The type of shafting which is to be used to position the character 16 on the print head 10 is not the particular subject matter of the present invention. The only requirement which is to be placed on the shafting is that it be sufficiently flexible at the point about which it is to bend so as to not introduce a significant amount of stored spring energy into the impact machanism. It is to be furthermore noted that the print head 10 is always to be pivoted from an initial upright vertical position so as to not bend the shafting away from the print medium which would have the adverse effect of introducing positive impact energy into the impact system.

FIG. 3-illustrates a type of shafting built which may be used with the present invention. A flexible coupling 54 connects a lower hollow shaft 56 to an upper hollow shaft 58. The hollow shaft structure 54 through 58 is part of a rotary drive system for the print head 10 that is fully disclosed in U.S. Application Ser. No. 94,144. A relatively small diameter shaft 60 is seen to extend through and to be guided closely by the hollow shafting 54 through 58. This results in a permissible bending of the shaft 60 only at the flexible coupling 54. The shaft 60 in flexing from an upright position does not introduce any positive impact energy into the print head 10. Since the shaft is relatively thin, the amount of energy expended in flexing it is relatively minor compared to that required for the impact printing itself. The small diameter shaft 60 functions to axially position the print head 10 according to the positioning apparatus disclosed in U.S. Application Ser. No. 94,144.

It is to be noted that the particular shafting used to position the print head 10 can take any number of different configurations according to the present invention. For instance a relatively small diameter shaft for both rotational and axial drive could be rotatably supported to either side of the pivotal axis 44 so as to flex or bend only about the pivot axis 44. The unguided portion of the positioning shaft which is to flex or bend must be adequately supported to either side in much the same manner as is the shaft 60 of FIG. 4.

Returning now to the impact mechanism of FIGS. 1 and 2, it is seen that a pair of biasing springs 62 and 64 are attached to the respective yoke arms 32 and 34 and to the carriage base 46. The biasing springs 62 and 64 normally retain both the yoke arms 32 and 34 against the armature plate 38 which isin turn retained against the energy sink pad 52. It is only during the various por- 65 OPERATION Referring to FIG. 4, when current is applied to the electromagnet 36 through a set of wires 66, the armature plate 38 rotates about the pivotal axis 44 and closes the one degree magnetic gap. This one degree of armature movement tilts the print head 10 one degree toward the print medium 20 as indicated. Referring now to FIG. 5, the yoke arm 32 and the print head 10 continue to rotate about the pivotal axis 44 due to the imparted velocity, V, in moving the previous one degree. This causes a separation 68 to occur between the yoke arm 32 and the armature 38 as shown in FIG. 5. The print head 10 and the yoke 26 are thus no longer externally driven during the last portion of flight toward the print medium 20. The only significant force acting on the yoke 26 and the print head 10 is that of the restoring forces within the biasing springs 62 and 64 which tend to decelerate the flight of the print head 10. The deceleration of the print head 10 causes the positioned character 16 to impact the print medium 20 at various energy levels depending on how far the print head 10 must travel before contacting the first fold of print medium.

Referring to FIG. 6, the amount of print energy present in the print head 10 as it travels toward the print medium 20 is seen to a function of the distance travelled before impact. The first portion of the print energy curve is seen to rise due to the initial acceleration of the armature 38 under the magnetic force of the electromagnet 36 as it moves into contact with the bottom of the magnet. This has been previously discussed in relation to FIG. 4. The second portion of the print energy curve is seen to decline due to energy extraction by the springs 62 and 64 as the print head 10 moves toward the print medium 20 as previously discussed in relation to FIG. 5. The actual distance travelled before impact will depend in any given situation on how many folds of print medium 20 are placed between the platen 22 and the print head 10. By appropriately choosing the magnetic force and/or gap distance to he travelled by the armature 38, the amount of print energy that is required for impact printing a large land character on a 6 part fold of print medium can be established. By choosing the appropriate springs 62 and 64, the amount of energy to be extracted from the print head 10 in moving from a normal contact with a 6 part fold to-a normal contact with a single part fold can be established. Thus by defining the appropriate parameters, one can arrive at an impact system which will provide the appropriate energy level for impact printing anything from a 6 part fold to a single fold of print medium.

It is thus seen that a free flight impact mechanism for a serial printer print head has been disclosed wherein the print head is adequately controlled during its free flight portion and is caused to adjustably strike a print medium ranging anywhere from a single part fold to a six part fold. The impacting is accomplished with a minimum number of moving parts which allows for a quick and responsive system.

What is claimed is:

1. In a serial printer containing a printhead which is to be impact printed with a print medium, impacting apparatus comprising:

a carriage;

a pair of mounting means extending upwardly from said carriage;

a pivotal axis means extending through said pair of mounting means;

means for supporting said print head above said carriage, said supporting means rotatably mounted on said pivotal axis means so as to rotate about said pivotal axis means from a rest position to a position whereby said print head contacts the print medium;

means for moving said support means, said moving means rotatably mounted only on said pivotal axis means;

means for limiting the rotation of said moving means about said pivotal axis means to a rotation which is a fractional part of the rotation of said supporting means about said pivotal axis means; and

means for normally biasing said support means against said moving means, said biasing means connected to said support means and to said carriage.

2. The apparatus of claim 1 further comprising:

means for establishing a normal rest position for said moving means from which said moving means begins to travel in moving said support means, whereby the rest position is an angular position of the moving means with respect to the pivotal axis means.

3. The apparatus of claim 2 wherein said moving means comprises:

a plate having an upper surface in contact with said support means and a bottom surface in contact with said resting means; and l a set of shoulders extending outwardly from said plate and rotatably mounted on said pivotal axis means.

4. The apparatus of claim 3 wherein said plate is magnetically conductive and said moving means further comprises:

an electromagnet attached to said carriage and positioned an angular gapped distance away from said magnetically conductive plate so as to cause said plate to travel in a pivotal are around said pivotal axis means when energized.

5. The apparatus of claim 4 wherein said biasing means comprises:

a set of coil springs each of which is attached to a repective yoke arm and to said carriage.

6. The apparatus of claim 4 wherein said supporting means comprises: 7

a yoke rotatable about said pivotal axis means; and

a set of yoke arms extending rearwardly away from said print medium and resting on the upper surface of said plate. 7

7. The apparatus of claim 6 wherein said means for establishing a rest position for said moving means comprises:

at least one upper surface contacting said plate and inclined withrespect to a horizontal line extending through said pivotal axis means.

8. The apparatus of claim 7 wherein said yoke arms contain inclined bottom surfaces being sloped at the angle of inclination of said upper surface of said means for establishing a rest position.

9. In a serial printer containing a print head which is rotatably and axially positioned for the subsequent impact printing of a positioned character with a print medium;

a carriage;

a pair of mounting means extending upwardly from said carriage;

a pivotal axis means extending through said pair of mounting means;

means for supporting said print head above said carriage, said supporting means rotatably mounted on said pivotal axis means, said supporting means being free to rotate angularly about said pivotal axis means a first angular rotational distance so as to impact print the positioned character with said print head; and

means for moving said support means a second angular rotational distance about said pivotal axis means wherein said second angular rotational distance is less than said first angular rotational distance.

10. The apparatus of claim 9 wherein said support means normally rests on said moving means, and said apparatus further comprises:

means, positioned beneath said moving means, for establishing a normal rest position for said moving means; and

means, positioned above said moving means, for stopping said moving means after said moving means has rotated said second angular rotational distance about said pivotal axis means from the normal rest position;

11. The apparatus of claim 10 wherein said support means and said moving means extend rearwardly away from the print medium; and said support means comprises:

a yoke rotatable about said pivotal axis means; and

a set of yoke arms extending rearwardly from said print medium and resting on said moving means, said yoke arms furthermore extending to either side of said means for stopping said moving means whereby said yoke arms are free from interference or limitation of movement by said stopping means.

12. The apparatus of claim 11 further comprising:

means for biasing said support means against said moving means, said biasing means connected to said support means and to said carriage.

13. The apparatus of claim 12 wherein said moving means is rotatably mounted only on said pivotal axis means and comprises:

a set of shoulders rotatably mounted on said pivotal axis means, each shoulder being adjacent to one of said mounting means; and

wherein said supporting means is rotatably mounted between said set of shoulders. 

1. In a serial printer containing a print head which is to be impact printed with a print medium, impacting apparatus comprising: a carriage; a pair of mounting means extending upwardly from said carriage; a pivotal axis means extending through said pair of mounting means; means for supporting said print head above said carriage, said supporting means rotatably mounted on said pivotal axis means so as to rotate about said pivotal axis means from a rest position to a position whereby said print head contacts the print medium; means for moving said support means, said moving means rotatably mounted only on said pivotal axis means; means for limiting the rotation of said moving means about said pivotal axis means to a rotation which is a fractional part of the rotation of said supporting means about said pivotal axis means; and means for normally biasing said support means against said moving means, said biasing means connected to said support means and to said carriage.
 2. The apparatus of claim 1 further comprising: means for establishing a normal rest position for said moving means from which said moving means begins to travel in moving said support means, whereby the rest position is an angular position of the moving means with respect to the pivotal axis means.
 3. The apparatus of claim 2 wherein said moving means comprises: a pLate having an upper surface in contact with said support means and a bottom surface in contact with said resting means; and a set of shoulders extending outwardly from said plate and rotatably mounted on said pivotal axis means.
 4. The apparatus of claim 3 wherein said plate is magnetically conductive and said moving means further comprises: an electromagnet attached to said carriage and positioned an angular gapped distance away from said magnetically conductive plate so as to cause said plate to travel in a pivotal arc around said pivotal axis means when energized.
 5. The apparatus of claim 4 wherein said biasing means comprises: a set of coil springs each of which is attached to a repective yoke arm and to said carriage.
 6. The apparatus of claim 4 wherein said supporting means comprises: a yoke rotatable about said pivotal axis means; and a set of yoke arms extending rearwardly away from said print medium and resting on the upper surface of said plate.
 7. The apparatus of claim 6 wherein said means for establishing a rest position for said moving means comprises: at least one upper surface contacting said plate and inclined with respect to a horizontal line extending through said pivotal axis means.
 8. The apparatus of claim 7 wherein said yoke arms contain inclined bottom surfaces being sloped at the angle of inclination of said upper surface of said means for establishing a rest position.
 9. In a serial printer containing a print head which is rotatably and axially positioned for the subsequent impact printing of a positioned character with a print medium; a carriage; a pair of mounting means extending upwardly from said carriage; a pivotal axis means extending through said pair of mounting means; means for supporting said print head above said carriage, said supporting means rotatably mounted on said pivotal axis means, said supporting means being free to rotate angularly about said pivotal axis means a first angular rotational distance so as to impact print the positioned character with said print head; and means for moving said support means a second angular rotational distance about said pivotal axis means wherein said second angular rotational distance is less than said first angular rotational distance.
 10. The apparatus of claim 9 wherein said support means normally rests on said moving means, and said apparatus further comprises: means, positioned beneath said moving means, for establishing a normal rest position for said moving means; and means, positioned above said moving means, for stopping said moving means after said moving means has rotated said second angular rotational distance about said pivotal axis means from the normal rest position.
 11. The apparatus of claim 10 wherein said support means and said moving means extend rearwardly away from the print medium; and said support means comprises: a yoke rotatable about said pivotal axis means; and a set of yoke arms extending rearwardly from said print medium and resting on said moving means, said yoke arms furthermore extending to either side of said means for stopping said moving means whereby said yoke arms are free from interference or limitation of movement by said stopping means.
 12. The apparatus of claim 11 further comprising: means for biasing said support means against said moving means, said biasing means connected to said support means and to said carriage.
 13. The apparatus of claim 12 wherein said moving means is rotatably mounted only on said pivotal axis means and comprises: a set of shoulders rotatably mounted on said pivotal axis means, each shoulder being adjacent to one of said mounting means; and wherein said supporting means is rotatably mounted between said set of shoulders. 